Strange coding in _mdfd_openseg()

Hello,

I think the following conditional code is misleading, and I wonder if
it would be better like so:

--- a/src/backend/storage/smgr/md.c
+++ b/src/backend/storage/smgr/md.c
@@ -1787,8 +1787,13 @@ _mdfd_openseg(SMgrRelation reln, ForkNumber
forknum, BlockNumber segno,
if (fd < 0)
return NULL;

- if (segno <= reln->md_num_open_segs[forknum])
- _fdvec_resize(reln, forknum, segno + 1);
+ /*
+ * Segments are always opened in order from lowest to highest,
so we must
+ * be adding a new one at the end.
+ */
+ Assert(segno == reln->md_num_open_segs[forknum]);
+
+ _fdvec_resize(reln, forknum, segno + 1);

/* fill the entry */
v = &reln->md_seg_fds[forknum][segno];

I think the condition is always true, and with == it would also always
be true. If that weren't the case, the call to _fdvec_resize() code
would effectively leak vfds.

--
Thomas Munro
https://enterprisedb.com